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Cold seep communities discovered at three previously unknown sites between 600 and 1000 m in Monterey Bay, California, are dominated by chemoautotrophic bacteria (Beggiatoa sp.) and vesicomyid clams (5 sp.). Other seep-associated fauna included galatheid crabs (Munidopsis sp.), vestimentiferan worms (Lamellibrachia barhami?), solemyid clams (Solemya sp.), columbellid snails (Mitrella permodesta, Amphissa sp.), and pyropeltid limpets (Pyropelta sp.). More than 50 species of regional (i.e. non-seep) benthic fauna were also observed at seeps. Ratios of stable carbon isotopes (δ13C) in clam tissues near -36‰ indicate sulfur-oxidizing chemosynthetic production, rather than non-seep food sources, as their principal trophic pathway. The 'Mt Crushmore' cold seep site is located in a vertically faulted and fractured region of the Pliocene Purisima Formation along the walls of Monterey Canyon (~635 m), where seepage appears to derive from sulfide-rich fluids within the Purisima Formation. The 'Clam Field' cold seep site, also in Monterey Canyon (~900 m) is located near outcrops in the hydrocarbon-bearing Monterey Formation. Chemosynthetic communities were also found at an accretionary-like prism on the continental slope near 1000 m depth (Clam Flat site). Fluid flow at the 'Clam Flat' site is thought to represent dewatering of accretionary sediments by tectonic compression, or hydrocarbon formation at depth, or both. Sulfide levels in pore waters were low at Mt Crushmore (ca 0.2 mM), and high at the two deeper sites (ca 7.011.0 mM). Methane was not detected at the Mt Crushmore site, but ranged from 0.06 to 2.0 mM at the other sites., Cited By (since 1996):108,
Invertebrates, CODEN: DRORE, ,

Big Creek Marine Ecological Reserve (BCER), located off the central California coast, has been closed to fishing since January 1994. We used side scan sonar and an occupied submersible to collect baseline information on species-habitat relationships, density, and species and size composition of fish inside and outside BCER. Forty-three dives were made in the fall of 1997 and 1998, at depths of 20-250 m. From 142 video transects, we identified over 70,000 fish from 82 taxa, including 36 species of rockfish. About 93% of the 25,159 fish inside BCER were rockfishes representing at least 20 species. Young-of-the-year rockfishes dominated rock outcrops in 20-90 m depth inside and outside BCER. Four distinct fish assemblages were associated with (1) fine, smooth sediment in deep water; (2) bedrock with uneven surface in deep water; (3) sand waves and shell hash in shallow water; and (4) boulders and organic habitats on rock in shallow water. There were no significant differences in fish density among locations (inside and outside BCER) and depths or between years. Density was significantly higher in high-relief rock habitat than in low-relief soft and mixed sediments, regardless of location. There were no consistent patterns of larger fish inside compared to outside the protected area. We recommend development of a monitoring program to continue these surveys after increased time of protection and with increased assessment effort in the appropriate habitats of economically valuable species. In addition, extending the boundaries of BCER seaward would protect habitats and fish in water depths greater than 100 m., Cited By (since 1996):18, , , Downloaded from: http://calcofi.org/publications/ccreports.html (05 June 14).

Impacts of bay floor disturbances on benthic habitats in San Francisco Bay,

Description

Approximately 120 km2 of San Francisco Bay were mapped using archived multibeam bathymetry data and another ∼40.5 km2 were mapped using recently acquired sidescan sonar data. Imagery was collected in several parts of San Francisco Bay, typically between 10 and 30 m. These data were interpreted into potential habitat types and further evaluated for natural (normally-) and human-induced disturbances. Ninety-one distinct potential habitats were identified, of which 74 were composed of soft, 12 of mixed, and 5 of hard, substrates. Bay floor sediment samples, collected by the US Geological Survey and the National Ocean Survey of the National Oceanic and Atmospheric Administration, were used to document substrate composition and document ("ground-truth") habitat interpretations. The sedimentological history of the region extends back to approximately 10 Ma with the initiation of a major sediment depocentre in the tectonic graben formed between the Hayward-Calaveras and San Andreas fault zones. Modern sedimentation from fluvial input and tidal scouring and deposition has resulted in a dynamic and complex bay floor. Strong currents have produced large sediment waves and dune fields, rippled sediment patches, and scoured channel floors and walls. Soft habitats composed primarily of mud and/or sand dominate the region, whereas hard rocky and mixed habitats are relatively rare and occur mainly in shallow areas adjacent to peninsulas and islands. Anthropogenic effects such as dredge material and debris-fields, borrow pits, dredged channels, and blasted bedrock knolls and normal disturbances such as sand waves are distinctly displayed in the data covering ∼63.5 km2 of area and delineated on the habitat maps. With the increasing demand for construction aggregate and development in the greater San Francisco Bay area, and the need to maintain and expand dredged channels and lower bedrock knolls to allow the safe passage of deeper draft vessels, many potential habitats will be impacted., , ,

Applying marine habitat data to fishery management on the US west coast,

Description

Recent experience in implementing legal requirements to designate and protect Essential Fish Habitat for groundfish off the US west coast is providing an opportunity to develop a feedback loop between science and policy for habitat- and ecosystem-based management that mirrors the traditional stock assessment/harvest management paradigm. The stock assessment/harvest management feedback loop dates back to the 1940s and has strongly influenced the development of the marine fishery management in frastructure and associated research programs. Assessment of marine habitat and the related establishment of regulatory policies by west coast fishery managers offer the potential for a similar feedback loop and the tailoring of research and infrastructure to improve the information available for decision-making., Cited By (since 1996):2,
Fish and Fisheries, ,

The Oak Ridge fault is a large-offset, south-dipping reverse fault that forms the south boundary of the Ventura Basin in southern California. Previous research indicates that the Oak Ridge fault south of the town of Ventura has been inactive since 200-400 ka ago and that the fault tip is buried by ∼ 1 km of Quaternary sediment. However, very high-resolution and medium-resolution seismic reflection data presented here show a south-dipping fault, on strike with the Oak Ridge fault, that is truncated at 80 m depth by an unconformity that is probably at the base of late Pleistocene and Holocene sediment. Furthermore, if vertically aligned features in seismic reflection data are eroded remnants of fault scarps, then a subsidiary fault within the Oak Ridge system deforms the shallowest imaged sediment layers. We propose that this subsidiary fault has mainly left-slip offset. These observations of Holocene slip on the Oak Ridge fault system suggest that revision of the earthquake hazard for the densely populated Santa Clara River valley and the Oxnard coastal plain may be needed., Cited By (since 1996):6, CODEN: BSSAA, ,

As global earthquake activity continues to impact Communities, infrastructure, and lives, the necessity of better identification and characterization of seismic hazards becomes ever clearer. The tragic 2011 Tohoku, Japan earthquake and tsunami increased the attention on critical coastal infrastructure projects exposed to earthquake hazards. Offshore faults are more difficult to identify and characterize than onshore faults. While multibeam bathymetric surveys can reveal surface geomorphologic expression of faults, seismic source characterization studies also require investigations of fault geometry in the subsurface. High-resolution offshore geophysical surveys can be a highly valuable tool for these tasks. Specifically, the use of high-resolution three-dimensional seismic reflection investigations can provide some of the most precise information about fault location, activity, and geometry. This work will discuss how the latest generation of ultra-high-resolution/high-fidelity marine seismic systems can be used to investigate sub-sea faults, and how it applies to complex geologic hazards to coastal infrastructure.

The application of geological and geophysical techniques in characterizing marine benthic habitats is increasing among fisheries biologists, marine geologists and fisheries managers. In this paper the results of a comprehensive sidescan sonar survey and seafloor observation/sampling program are applied to characterize fish habitats in a geologically complex volcanic region. Sidescan sonographs, interferometric bathymetric data, and in situ observations using the submersible Delta were used to identify and describe rockfish (Scorpaenidae, genus Sebastes) habitats of the continental shelf seaward of Kruzof Island in southeast Alaska. A major feature of this part of the continental shelf is the offshore Edgecumbe lava field. Mount Edgecumbe, a Holocene shield volcano, last erupted ca. 7000 years ago when it spread lava upon aflat glaciated surface and covered at least 600 km2 of seafloor and coastal plain west of Kruzof Island. The lava surface exhibits well-defined and little-eroded aa and pahoehoe lava, lobate lava fronts, compression ridges, collapsed lava tubes and volcanic cones that mark the distal end of Mount Edgecumbe's southwest rift. The presence of these features, along with the recovered vesicular basalt samplesftom the seafloor and the absence of pillow lava, suggests that the lava field was formed either terrestrially or in a shallow marine environment and, based on the depth of the outer limits of the field, has subsided at least 300 m. The offshore Edgecumbe lava field is defined as a marine benthic megahabitat that contains a variety of mesohabitats conducive to the habitation of rockfishes. The geologic features within this megahabilat give rise to mesohabitats that consist of pinnacles, caves, boulders, cobbles and pebbles, cracks and crevices, and ridges. The diversity and distribution of rockfish species appear to be related to mesohabitat type and depth, with the presence of suitably-sized refuge spaces a key to the occurrence of demersal rockfish. In boulder and ledge areas, such as those that occur around the pinnacles (volcanic cones), yelloweye rockfish (Sebastes ruberrimus), tiger rockfish (S. nigrocinctus), lingcod (Ophiodon elongatus), prowfish (Zaprora silenus) and sharpchin (S. zacentrus) are frequently present. On the pinnacles' crests where broken rock, ledges and platforms exist, the fish assemblage includes lingcod, quillback (S. maliger), Puget Sound (S. emphaeus) and young-of-the-year rockfishes. Similar assemblages of fish inhabit the caves and rubble-strewn floors of collapsed lava tubes. Elsewhere on the lavafield, rosethorn (S. helvomaculatus) and pygmy (S. wilsoni) rockfishes inhabit cracks and crevices in the lava flows and also occur in small boulder, cobble andpebble terranes. Compressional ridges with broken and angular boulders and slabs are frequented by yelloweye and tiger rockfishes. Pelagic rockfishes such as dusky (S. ciliattis), black (S. melanops) and yellowtail (S. flavidus) are found in schools and individually in areas of high relief, such as ridges and angular outcrops of rocks, and schools of pygmy rockfish and unidentified juvenile rockfishes inhabit most mesohabitats from pinnacles to cobble fields., Rocks & Cores, ,

The effects of dredge material disposal on marine benthic habitats of the Santa Cruz Bight, California,

Description

In March, 2001, the Santa Cruz Small Craft Harbor was permitted to dredge some mixed sand and mud (silt and clay) from the upper harbour onto the surf zone at Twin Lakes Beach. A monitoring program was conducted to determine if any sedimentary changes occurred in nearshore benthic habitats of the Santa Cruz Bight during the experimental dredging period. To map the spatial distribution of benthic habitats at risk, and to determine if sedimentary changes occurred due to harbour dredging, multibeam bathymetry surveys and sediment sample data were collected before, during and after the dredging. These data were analyzed and interpreted into two benthic habitat maps and compared using a new GIS mapping technique to quantify areas of sediment erosion and deposition on the Santa Cruz Bight seafloor. The integration and analyses of the data collected over the monitoring period indicates that the muddy upper harbour sediment did not significantly disturb or change the grainsize characteristics of nearshore marine benthic habitats in the Santa Cruz Bight., Cited By (since 1996):1, Rocks & Cores, ,

The application of marine geophysics and GIS techniques to the characterization of benthic habitats has increased the ability of fisheries managers to assess distribution and habitat types beyond common practices. We report upon a 150 kHz sidescan sonar survey offshore of Kruzof Island, Alaska undertaken to characterize rockfish (Sebastes) habitat. Using GIS, MapGrafix and Map*Factory we determined the percentage of seafloor cover that exists in our survey area. Bathymetry in the study area was determined with sidescan interferometry. All XYZ data were gridded using Surfer and plotted in shaded relief, bathymetric contour, and 3-dimensional formats. Contoured bathymetry was used as an overlay in MapGrafix. Small sub-areas were extracted from the bathymetric data for closer study, and gridded in Surfer. Areas of the mosaic where backscatter patterns were not distinct were verified with hand samples and video collected with the submersible Delta. The use of submersibles for verification of interpreted lithologies and surface textures enables a high degree of accuracy for the interpretations. Lithotypes were lumped into larger groups based on morphology and fish associations with different morphologies verified using the submersible. The accuracy of digital maps from high-resolution sidescan sonar data allows a close quantification of the areal extents of these important features, directing the application of management strategies to critical areas., Cited By (since 1996):24, Oceanography, CODEN: OCACD, ,

Construction of digital potential marine benthic habitat maps using a coded classification scheme and its application,

Description

Recent advancements in remote-sensing geophysical technology have enabled the imaging of deep seafloor regions, and the construction of detailed maps depicting potential marine benthic habitats. The recent and severe declines in many groundfish stocks, and the degradation of associated seafloor habitats make these maps of critical importance to the identification of essential fish habitat, and the facilitation of habitat-based management, through the establishment of marine protected areas. However no standard approach to mapping deep-water (>30 m) marine benthic habitats has been established and endorsed by the scientific community, even though several different deep-water habitat characterization schemes exist or are evolving. In this paper, a classification scheme, including an attribute code, for mapping potential marine benthic habitats is presented in an attempt to establish a standard technique to facilitate reproducibility of habitat designations and comparisons of deep-water marine benthic habitats worldwide. This scheme has been developed over more than 15 years of mapping seafloor habitats. One of the main strengths of the scheme is versatility and ease of use because it can be applied to any seafloor environment and is directly adaptable to use with Geographic Information System (GIS) programs. The habitat-mapping scheme presented here is based on physiography and scale, induration (hardness of substrate), and geomorphology. The attribute code associated with this scheme consists of seven primary characters that can be used to represent: 1) physiography and depth (i.e., megahabitat), 2) substrate induration, 3) geomorphology (i.e., meso- and macrohabitat), 4) modifiers for texture, lithology, bedform and biology, 5) seafloor slope or inclination, 6) seafloor rugosity, and 7) geological unit, represented by standard geological symbols. The latter three characters are optional and are included only when slope and rugosity can be calculated and when the geology is known. Further an additional attribute code is presented for use in distinguishing potential habitat types from video and photographic data that consists of two primary characters: 1) geologic or substrate attributes, and 2) biological attributes., Cited By (since 1996):2
Fish and Fisheries, ,

The use of geophysical survey data in fisheries management: A case history from southeast Alaska,

Description

The Alaska Department of Fish and Game (ADF&G) has been conducting a habitat-based stock assessment of yellow-eye rockfish (Sebastes niberrimus) in the eastern Gutf of Alaska since 1989. Yelloweye rockfish occur in rugged rocky terrain on the continental shelf, and are an important commercial species taken in directed, and by-catch bottom-long-line fisheries. The biomass of yelloweye rockfish is derived as the product of density, average weight, and area of habitat. Density is based on line-transect surveys conducted from an occupied submersible. Area estimates of yelloweye habitat are based on the probable distribution of rocky habitat inshore of the 200 m bathymetric contour. Information used to identify rocky habitat include sidescan and multibeam sonar data (ground-truthed using direct observation from the submersible) and commercial logbook data from the directed fishery. In areas with multibeam or sidescan sonar data, the area of rockfish habitat is delineated based on defined substrate types within the mapped area. For areas without these geophysical datasets, position data from commercial fishery logbooks is used. In areas with both logbook and geophysical data, areas of habitat generally overlap but are not identical. Logbook data is mandatory, but self-reported, and may not always be accurate. Geophysical surveys reveal the extent of all rocky habitats, while fishermen target areas of prime habitat. Limiting of surveys to prime habitat may result in inaccurate stock assessments because density may remain stable in the prime habitat, while declining in surrounding habitats. By assessing fish densities in all rockfish habitats, as delineated by geophysical surveys, a better indicator of stock condition is possible. Further unlike logbook data, multibeam data allows us to clearly define boundaries of prime habitats, relevant to management decisions regarding marine reserves or to definition of management units., , ,

A standard, universally useful classification scheme for deepwater habitats needs to be established so that descriptions of these habitats can be accurately and efficiently applied among scientific disciplines In recent years many marine benthic habitats in deep water have been described using geophysical and biological data. These descriptions can vary from one investigator to another, which makes it difficult to compare habitats and associated biological assemblages among geographic regions. Using geophysical data collected with a variety of remote sensor systems and in situ biological and geologic observations, we have constructed a classification scheme that can be used in describing marine benthic habitats in deep water., Cited By (since 1996):117, Rocks and Cores, CODEN: OCACD, ,

Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean,

Description

The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km 2 in the open equatorial Pacific Ocean with iron. This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production. Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturaly enriched in iron. These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean., Cited By (since 1996):749, Oceanography, CODEN: NATUA, ,